Experiments were performed on the lateral transport kinetics of wetting layers. Optically excited surface plasmons were used to study both the spreading behaviour of silicon oil and the equilibration dynamics of ethanol. The precursor film profiles of silicon oil were found to agree well with the theory of viscous flow of nonvolatile liquids. For ethanol, evaporation effects and viscous transport could be observed separately. Apparently, the viscous transport is suppressed by almost two orders of magnitude. Possible explanations are discussed.